Effect of 4-hydroxybenzoic acid on CO2 separation performance of poly(ethylene oxide) membrane

We successfully prepared highly selective poly(ethylene oxide) (PEO) membranes containing 4-hydroxybenzoic acid for CO2 separation. Because 4-hydroxybenzoic acid contains a benzene ring that acts as a barrier against gas transport and also contains hydroxyl and carboxyl groups that enhance the solubility of CO2 molecules, the incorporation of 4-hydroxybenzoic acid was expected to substantially increase the CO2/N-2 selectivity. Indeed, when 4-hydroxybenzoic acid was incorporated into the PEO matrix, the CO2/N-2 selectivity increased from 1.8 to 23 with a CO2 permeance of 8.8 GPU. The coordinative interactions of 4-hydroxybenzoic acid in the PEO matrix were confirmed by Fourier transform infrared spectroscopy. Additionally, thermogravimetric analysis verified that 4-hydroxybenzoic acid was strongly stabilized in the polymer matrix.